This was a single centre, double-blind, randomised, placebo-controlled, single-graded-dose, crossover study with five single-dose treatment periods. The washout period between doses was 15±2 days. For each of the five treatment periods, volunteers were to be admitted at the UFH on the day before the treatment day. On each treatment period, the pre-dose assessment were to be completed, BIA 3-202/Placebo was to be administered concomitantly with the dose of Sinemet® 25/100 and post-dose assessments were to be completed. Subjects were discharged 30 h post-dose. Subjects should attend five treatment periods and were to receive a different dose of BIA 3-202 or placebo during each of these treatment periods.